Corrosion protective composition



Patented May 16, 1944 CORROSION PROTECTIVE COMPOSITION Edward J. Jahn,Edwardsville. Ill., assignor to Shell Development Company, SanFrancisco.

Calif., a corporation of Delaware No Drawing.

Application July 21, 1941,

Serial No. 403,393

9 Claims. (Cl. 106-14) This invention relates to non-gaseous hydrocarboncompositions possessing corrosion-protecting properties, and moreparticularly is concerned with such compositions containing dissolvedsmall amounts of high molecular weight carboxylic acids havinganti-corrosive properties.

It is already known that the addition of small amounts of certainoil-soluble polycarboxylic acids or hydroxy aromatic carboxylic acidsimpart to lubricating oils and other non-gaseous hydrocarbons, such asgasoline. Diesel fuels, kerosene, gas oil. lubricating oils, petrolatum.petroleum plastics. etc., strong corrosion-protective properties. Acidspossessing this property are those having at least 12, and preferably 20or more carbon atoms, and it is desirable that their active radicals, i.e., the several carboxylic radicals. or carboxylic and hydroxylradicals. as the case may be. be as close to each other as possible andbe separated from each other by not more than 4, and preferably by notmore than 2, intervening atoms. Stability of the acids under conditionsto which the compositions are exposed is an added requirement.

Among the polycarboxylic acids which are particularly useful forpreventing corrosion are the following: polymerized and hydrogenatedfatty acids, e. 'g., voltolized and hydrogenated lauric, pairnitic,stearic. oleic. ricinoleic. etc., acids. unsaturated fatty acidspolymerized with a halide polymerization catalyst such as BF: andsubsequently hydrogenated; alkyl phthalic acids, alkylated naphthalenedcarboxylic acids, such as .alkyl naphthalic acids: various alkylatedaliphatic polycarboxylic acids such as succinic. glutaric. :2.

adipic, pimelic, suberic. azelaic, tricarbally'nc, etc., acids. Ifdesired, these acids may contain various substitution rad cals ashydroxyl. ether, amino, nitro, hydrosulfide. sulfide,- halide. etc.,radicals, the most important limiting factor being the necessarystability. In general, it is r ferred to use n saturated aliphaticdicarboxylic acid having the carboxyl radicals as close to each other aspossible and as is consistent with the requirement for stability.Particularly effect ve are alkyl succinic acids having at least 16, andpreferably 20 to 40 carbon atoms. Malonic acid and its alkyl derivativesare known to be unstable and. therefore, cannot be used.

0f the hydroxy carboxylic acids, hydroxy aromatic carboxylic acids inwhich the hydroxy radical is directly attached to the aromatic nucleusare most useful; for example, various alkyl phenol or naphtholcarboxylic acids wherein the carboxylic acidradical is attached to thenucleus di.

rectly or through a carbon linkage, e. g.. alkyl salicylic acids,preferably those whose alkyl radicals contain 12 or more carbon atoms,hydroxy naphthoic acids or hydroxy aromatic fatty acids such as may beproduced by coupling a phenol or a naphthol, etc., with oleic or otherunsaturated fatty acid or with rosin acid, etc., in the presence ofaluminum chloride.

It has been found in the past that the mechanism by which the aboveacids protect materials from corrosion is one of formation of aprotective film which adheres to the metal more or less tenaciously.However, this film formation, and more particularly the anchoring of thefilm on the metal surface, appears to be a very slow process, oftenrequiring 24 hours or longer. It was then discovered that the presenceof water would greatly accelerate the rate of formation as well as thetenacity of the protective film. It was therefore thought that thepresence of at least small amounts of water was essential for theformation of the film.

It is an object of this invention to produce corrosion inhibitinghydrocarbon compositions which deposit on metals a protcctivefilm withina r-asoriably short time. It is another purpose to n 'dice this filmwith the aid of certain carboxylic acids without the aid of water; andit is a purpose to produce with these acids and without 'water such aprotective film which has a tenacity greater than that obtainedheretofore even in the presence of water.

I have discovered that the'rate of formation of the protective film canbe accelerated and its tenacity be materially increased by the presenceof certain auxiliary compounds other than water. More particularly Ihave found that this improvement can be achieved either by using amixture of the above two types of corrosion-inhibiting acids or else byemploying in conjunction with eithe certain oil-soluble. substantiallywater-insoluble monocarboxylic acids or esters of monocarboxylic acidswhich by themselves have little, if any. corrosion-protective powers andwhich preferably are free from ether-forming hydroxyl radicals postioned in close proximity to the acid radical. Su table acids of thelatter type are, for example, fatty acids having'at least 7, andpreferably from 10 to 30. carbon atoms. e. g.. lauric, stearic, oleic.arachic. behenic. ricinn e'c. eta. acids. wool fat acids. carboxylicacids produced by oxidation of parafiin wax, naphthenic acids,rosinaclds such as abietic acid, hydrogenated abietic acids. acidsderived from talloil. benzoic acid, alkyl benzoic acids, naphthoicacids, phenyl acetic acid. aromatic fatty acids, etc. Esters suitablefor our purpose are particularly those combining monohydric alcoholswith monocarboxylic acids, which esters possess at least 6 carbon atoms,for example, butyl, hexyl, octyl, decyl, oleyl, stearyl, etc., acetates,propionates, butyrates, valerates, laurates, palmitates. oleates,stearates, rosinates, abietates, naphthenates, benzoates, naphthoates,etc., corresponding methyl, ethyl, propyl, isopropyl esters having 6 ormore carbon atoms, etc.

The enhancing effect of the monocarboxylic acids and their esters seemsto be quite specific in that acids other than carboxylic' acids such asvarious organic phosphorus acids, sulfonic acids, etc., have an eflectjust opposite, that is, decreasing the protective effect of the primarycorrosion inhibitors and in many cases causing rapid corrosion in spiteof the presence of the inhibitor.

The useful amounts of the corrosion-inhibiting polycarboxylic acids orhydroxy aromatic carboxylic acids used in various hydrocarboncompositions are known to vary between fairly wide limits, depending notonly on the particular use to which the composition is to be put, butalso depending on the susceptibility of the hydrocarbon compositiontoward these acids. In general, the presence of large amounts ofpetroleum resins. gums, etc., has a retarding eifect. Thus, indistillate oils as gasoline, kerosene, diesel fuel oils, gas oil, lightlubricating oils, etc.,

amounts of the active corrosion-inhibiting acids between .001 %-.1%, arenormally ample. In bright stocks amounts from .1% to about 1% may berequired, and in petroleum plastics, such as albino asphalts, or inpetrolatums, suitable amounts may range from below .1% to above 1% andmay be as high as %-10%.

The amounts of the auxiliary acids or esters which I add may be of anorder similar to those of the corrosion-inhibiting acids. Thus theamount of auxiliary compounds may be about the same as, or smaller orhigher than, that of the main inhibitor. In general, however, I preferto use quantities below 1%.

The importance of rapidly forming a tenacious corrosion-protecting filmis, of course, manifest. For example, when machining metal parts to veryaccurate dimensions, the machined surface must be immediately protectedagainst rusting as soon as it is finished. Thus, simple dipping of theobject into a suitable oil should have a complete protective effect sothat subsequent handling does not cause local rusting.

Likewise, under many circumstances it is very desirable that water beabsent, for water being substantially insoluble in hydrocarbons tends toform a separate phase which requires strong agitation in order to makeit effective as an accel erator for the active corrosion-inhibitingacids. This may lead to emulsion troubles. The presence of mutualsolvent for oil and.water does not always solve this difficulty,inasmuch as the mutual solvent may be extracted from the hydrocarboncompounds in, contact with large amounts of water, as a result of whichtwo separate layers are formed again.

The following examples illustrate my invention:

tested by two tests, a corrosion test and a film tenacity test asfollows:

Corrosion test-A clean steel strip is immersed in the well stirred oilkept at 167. F. After 80 minutes, 10% based on the volume of the oil.

, of an aqueous 2% NaCl solution is added. The

steel strip is removed from the stirred mixture after 48 hours,inspected visually and the extent of rusting recorded. 1

Film tenacity test-Two clean steel strips are immersed in the oil for 30minutes. They are transferred then to beakers holding stirred distilledwater; one kept at room temperature, the other at 167 F. The number ofhours elapsed until rusting starts are recorded.

Results were as follows:

Fllmttitiecity Alkyl Corrosion test succinio Fatty acid in 2% NaCl acidsolution At room At temperai67 F. ture hrs. hrs.

01; cent N one l0 rustcd.. 5

. 0.27 stearic acid. 20 I 0. oleic acid". .do 48 i0 None Completelyrusted. .027 stearic acid.. 107 rusted .01 naphthenic acid 25 a rusted"l Rusting started in less than 1 hr. Equivalent weight=342.

The addition oi? the auxiliary acids or esters to hydrocarbon oilscontaining the primary anticorrosives is of greatest importance whendealing with well-refined hydrocarbon compositions. Conventionalrefining methods, such as acid and alkli treatment, solvent extraction,hydrogenation, etc., raise the susceptibility of the hydrocarbons to theprotective action of the primary anti-corrosives on the one hand, but onthe other hand, remove naphthenic and other monocarboxylic acids whichmay naturally be contained in the hydrocarbons in small amounts andwhich enhance the action of the primary anti-corrosives. However, evenif small amounts of naphthenic and similar acids are naturally present,in general the addition of further amounts of the auxiliary acids oresters of the type described is beneficial.

I claim as my invention:

1. A corrosion-inhibiting composition comprising non-gaseoushydrocarbons containing amounts sufilcient to inhibit corrosion each ofa polycarboxylic acid havingcorrosion-inhibiting properties, and of anauxiliary oil-soluble, waterinsoluble compound having but littlecorrosion inhibiting power selected from the group consisting ofhydrocarbon monocarboxylic acids free from ether-forming hydroxylradicals and esters thereof with monohydric alcohols.

2. The composition of claim 1 wherein said polycarboxylic acid is analkyl succinic acid having at least 16 carbon atoms.

3. The composition of claim 1 wherein said polycarboxylic acid is analkyl succinic acid having between 20-40 carbon atoms.

4. The composition of claim 1 wherein said hydrocarbon is a lubricatingoil.

5. A corrosion-inhibiting composition comprising non-gaseoushydrocarbons containing amounts sufficient to inhibit corrosion each ofa corrosion-inhibiting acid selected from the group consisting ofpolycarboxylic acids and hydroxy aromatic carboxylic acids having atleast 12 carbon atoms, and of an oil-soluble, water-insoluble,hydrocarbon monocarboxylic acid free from ether-forming hydroxylradicals.

6. A corrosion-inhibiting. composition comprising non-gaseoushydrocarbons containing amounts sumcient to inhibit corrosion each of acorrosion-inhibiting acid selected from the group consisting ofpolycarboxylic acids and hydroxy aromatic carboxylic acids, whose activeradicals are separated from each other by not more than 4 carbon atoms,having at least 12 carbon atoms and of a fatty acid having at least 7carbon atoms.

7. A corrosion-inhibiting composition comprising non-gaseoushydrocarbons containing amounts sufiicient to inhibit corrosion each ofa, corrosion-inhibiting acid selected from the group consisting ofpolycarboxylic acids and hydroxy aromatic carboxylic acids, whose activeradicals 20.

are separated from each other by not more than 4 carbon atoms, having atleast 12 carbon atoms and of a naphthenic acid having at least 7 carbonatoms.

8. A corrosion-inhibiting composition com-, prising non-gaseoushydrocarbons normally free small amounts of the added compounds rangefrom about .001 to 1%.

EDWARD J. JAHN.

